The first thing you need to determine is the measure of each interior angle or exterior angle. According to your problem, each interior angle is 108 degrees greater than each exterior angle. Thus,
x - measure of each exterior angle
x + 108 - measure of each interior angle
Since the interior and exterior angle form a linear pair, then we have
x + x + 108 = 180
2x = 72
x = 36
Thus, the measure of each exterior angle is 36 degrees.
Now, we know that the total measure of all exterior angles should add up to 360. Since we have a regular polygon here, then we have equal measures for all exterior angles. We have
n * 36 = 360
n = 10
Thus, your [regular] polygon has 10 sides, or is a decagon.
Hope this helps!!!!!